Such sealing arrangements are used, for example, in control devices, such as exhaust gas recirculation flap valves, for controlling a recirculated exhaust gas flow in commercial vehicles, where large quantities of exhaust gas must be supplied to the engine in a precisely controlled manner. It is necessary here to prevent the intrusion of exhaust gas into the bearings and, further, to prevent the gas from flowing through the bearing bore out into the atmosphere.
DE 10 2006 054 041 B3 discloses an exhaust gas control device comprising a housing in which an exhaust gas recirculation channel is formed that is controlled by a flap. This flap is driven by an electric motor via a transmission unit and is arranged for rotation on a shaft that is supported in bearing bores formed in the housing defining the channel. In order to prevent the intrusion of exhaust gas, and thus soot, into the bearings, and to simultaneously prevent a leakage gas flow to the outside, the housing is provided with a bore leading from the front side of the flap out from the channel to the rear side of the bearing and into the bearing bore. A sealing flow thus prevails on the rear side of the bearing that leads to a pressure balance with the inside of the channel so that the exhaust gas flow is not drawn into the bearing. To the outside, sealing is provided by means of a sealing disc abutting against a step of the bearing bore. This sealing disc is pressed against the step of the bearing bore by means of a spring via a collar bush and a sliding bush arranged between the collar bush and the sealing disc. The sliding bush serves to reduce friction, whereas a radially directed escape of a leakage flow is supposed to be prevented by the sealing disc and an escape is intended to be realized in the axial direction along the shaft via the axial extension of the collar bush which therefore forms a very narrow and long gap with the shaft.
It has, however, been found that such a design is insufficient with respect to the leakage values. The necessity of precise manufacturing furthermore results in high production costs.